Electro-photographic process using a liquid developer containing a polymeric dye

ABSTRACT

LIQUID DEVELOPER COMPOSITIONS FOR USE IN DEVELOPING ELECTROSTATIC CHARGE PATTERNS ARE FORMED OF AN ELECTRICALLY INSULATING ORGANIC CARRIER LIQUID HAVING DISPERSED THEREIN MARKING PARTICLES COMPRISED OF A POLYMERIC DYE HAVING A LINEAR BACKBONE CHAIN TO WHICH ARE ATTACHED PENDANT SIDE CHAINS CONTAINING A CHROMOPHORIC MOIETY.

United States Patent 3,743,503 ELECTRO-PHOTOGRAPHIC PROCESS USENG ALIQUID DEVELOPER CONTAINING A POLY- MERIC DYE Martin Goldman, Jerusalem,Israel, and Stewart H. Merrill, Rochester, N.Y., assignors to EastmanKodak Company, Rochester, N.Y.

No Drawing. Filed Feb. 24, 1970, Ser. No. 13,826

Int. Cl. G03g 13/00, 13/12 US. Cl. 96-1 8 Claims ABSTRACT OF THEDISCLOSURE Liquid developer compositions for use in developingelectrostatic charge patterns are formed of an electrically insulatingorganic carrier liquid having dispersed therein marking particlescomprised of a polymeric dye having a linear backbone chain to which areattached pendant side chains containing a chromophoric moiety.

This invention relates to electrophotography and more particularly, tothe development of electrostatic images using liquid developmenttechniques and compositions.

In electrophotography, it is known to use an element comprised of asupport having on it a layer of a photoconductive composition comprisinga resinous binder and a photoconductor, either organic or inorganic,which in the dark will accept and retain an electrostatic charge Aftercharging, such an element is then exposed in any suitable manner so asto vary the charge thereon in accordance with the relative energyreceived by the element during the exposure. After exposure the elementis usually developed by applying thereto a charge powder which is drawnto the element in conformity with the charge pattern produced byexposure. The powder is then fixed or fused in some manner thusproducing a powder image.

One of the difiiculties with this type of development has been theinability to uniformly distribute the powder over the element. If thepowder is unevenly applied, the image will similarly be formed in anuneven manner thus resulting in copy which is not a true representationof the original. Another difficulty is fixing the powder on the elementin a permanent manner which is normally accomplished by including aresin in the powder and subjecting the deposited powder to heat. Also itis difficult to obtain high resolution with powder developers.

Many of the disadvantages of dry powder developers,

such as dust, poor resolution, uneven distribution, etc., can be avoidedby the use of a liquid developer. Liquid developers, such as thosedisclosed previously in US. Pat. No. 2,907,674, are usually composed ofan insulating carrier liquid, a pigment such as carbon black and a resinto bind the pigment. However, when the pigment is deposited in animagewise fashion, it scatters unabsorbed light rather than transmittingit. Such scattering of light makes pigment-containing developers of thistype unsuitable for possible application in a multicolor subtractiveprocess.

A further difiiculty with pigment-containing liquid developers of thistype is that the pigment and the resin binder do not necessarily havethe same electrostatic charge polarity. Such bicharging can result inunwanted background density in images prepared from these developers.Still another problem encountered is that the pigment and the binder arenot always depleted at the same rate. This latter problem results in acontinually changing developer concentration with use. Such a conditionis highly undesirable in that each of a series of images developed inone developer solution will not be uniform in quality. Still anotherproblem that is sometimes encountered is that of the color leaching outof developed images.

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It is, therefore an object of this invention to provide new liquiddevelopers for electrostatic charge patterns.

It is another object of this invention to provide novel liquiddevelopers for forming colored images which absorb most incident light.

It is a further object of this invention to provide novel liquiddevelopers in which the binder and colorant are depleted during use atthe same rate.

Still another object of this invention is to provide methods forpreparing novel liquid developers containing substantially transparent,non-leachable colored dyes.

These and other objects of the invention are accomplished by preparing aliquid developer composition comprised of a carrier liquid containing apolymeric dye. In general, the polymeric dyes used in this invention arecomprised of a linear backbone chain having attached thereto pendantside chains containing a chromophoric moiety. The polymeric dyes of thisinvention are typically prepared by forming a polymeric coupler which isthen reacted with a suitable material to form the polymeric dye.

By polymeric couplers are meant polymers having nuclei which are capableof coupling with, for example, the oxidation products of color couplingaromatic primary amino developing agents such as formed on developmentof silver salt images to form an azomethine dye. Such polymeric couplersalso include polymers having nuclei which are capable of coupling withdiazotized aromatic amines to form azo dyes. Nuclei of the above typeare well known in the dye art and color photography art. They aresometimes called color-forming couplers, colorformers, couplingcomponents, etc. These dye intermediate nuclei or coupling nucleigenerally have as the active coupling group one of the following: (a) anactive openchain methylene group; (b) an active cyclic methylene group;and (c) a phenolic nucleus bearing an active methine group. Of course,the hydrogen atom at the coupling position of the coupler can bereplaced by a moiety which is readily eliminated in the couplingreaction, e.g., halogen, sulfonic acid, carboxylic acid, etc. Yellowcouplers usually contain group (a) above, magenta couplers generallycontain group (a) or (b) while cyan couplers typically contain group(c).

In a-typical method of preparing a polymeric coupler, a suitable firstvinyl monomer and a vinyl-containing dye intermediate or color-formerare polymerized together to form a hydrophobic polymeric coupler havinga linear backbone chain with pendant side chains attached theretocontaining a color-forming nucleus. In general, the first vinyl monomer,which contains no color-former can be selected from a wide variety ofmaterials depending upon the physical properties desired in the finalpolymer. Useful monomers would include styrene, including substitutedstyrene having such substituents as an amino radical and alkyl radicalspreferably having about 4 to 18 carbon atoms; alkyl acrylates havingfrom about 4 to 18 carbon atoms in the alkyl moiety such as isobutyl,pentyl, hexyl, decyl, dodecyl, pentadecyl, octadecyl acrylates, e'tc.;vinyl acetate; vinyl chloride; vinyl alkyl ethers having from about 4 to18 carbon atoms in the alkyl moiety such as isobutyl, pentyl, hexyl,decyl, dodecyl, pentadecyl, octadecyl, etc.; alkyl methacrylates havingfrom about 4 to 18 carbon atoms in the alkyl moiety such as isobutyl,pentyl, hexyl, decyl, dodecyl, pentadecyl, octadecyl methacrylates,etc.; and similar vinyl monomers. Mixtures of these materials as well asmixtures of the above monomers with alkyl acrylates, alkyl methacrylatesand vinyl alkyl ethers having from 1 to 3 carbon atoms in the alkylmoiety and with vinyl chloride, vinyl acetate, etc., are also useful.Preferred monomers contain alkyl moieties containing from about 4 to 18carbon atoms.

Monomers containing these longer alkyl radicals produce polymeric dyeshaving an enhanced compatibility with the hydrocarbon carrier liquidsused in forming the liquid developers of the present invention. Ofcourse, mixtures of a predominant amount of the preferred monomers withmonomers which do not contain the longer alkyl radicals are also useful.

The second vinyl monomer used in forming the polymeric couplers is, ingeneral, similar to the first vinyl monomer, only attached thereto is asubstituent which contains a color-forming nucleus. This color-formingnucleus can be (a) an active open chain methylene group, (b) an activecyclic methylene group or (c) a phenolic nucleus having an activemethine group attached. The first and second monomers are thencopolymerized by typical vinyl polymerization techniques to form asuitable polymeric coupler. Of course, useful polymeric couplers can beprepared by forming a linear polymer having reaction sites wherecolor-forming substituents can subsequently be attached. By whatevermeans formed, the resultant polymeric couplers are comprised of a linearbackbone chain having pendant side chains containing as the couplingunit one of the following: (a) an open chain methylene coupling moiety,(b) a cyclic methylene coupling moiety and (c) an activemethinesubstituted phenolic coupling moiety.

The polymeric couplers described above can be readily converted topolymeric dyes useful in developers of the present invention. Typically,the polymeric couplers are reacted with oxidation products of colorcoupling aromatic primary amine developing agents such asp-phenylenediamines and p-aminophenol. Typical aromatic primary aminedeveloping agents include:

N,N-diethyl-p-phenylenediamine, Z-arnino-S-dieth'ylamino toluene,N-ethyl-[i-methanesulfonamido-ethyl-3-methyl-4-amino aniline,4-arnino-N-ethyl3-methyl-N- p-sulfoethyl) aniline, 4-amino-N-ethyl-3-methoXy-N- (-,8-sulfoethyl aniline, 4-amino-N-ethyl-N- S-hydroxyethyl)aniline, 4-amino-N,N-diethyl-3-hydroxyrnethyl aniline,4-a1nino-N-methyl-N- fl-carboxyethyl) aniline, 4-amino-N,N-bis(fl-hydroxyethyl) aniline, 4-amino-N,N-bis(fi-hydroXyethyl)-3-methylaniline, 3-acetamido-4-amino-N,N-bis ,B-hydroxyethyl) aniline,4-amino-N-ethyl-N-(2,3-dihydroxypropyl)-3-methyl aniline sulfate salt,4-amino-N,N-diethyl-3- 3 -hydroxypropoxy) aniline, and

the like. 1

The resultant polymeric dyes are azomethine dyes.

Similarly, the polymeric couplers above can be reacted with diazotizedaromatic amines (diazonium salts) to form azo dyes. Advantageousdiazonium salts include benzene diazonium salts such as those having theformula:

wherein M is either:

(1) a hydrogen atom,

(2) a halogen atom,

(3) an aryl radical,

(4) an amino radical including substituted amino radicals which can becyclic radicals including the amino nitrogen atom and other hetero atomssuch as oxygen, sulfur, nitrogen, etc.,

(5) a mercapto radical, or

(6) an alkyl or aryl thioether radical, and

Z is an acid anion. These compounds can also be substituted on one ormore of the nuclear benzene carbons with, for example, at least one ofeither a halogen atom,

an aliphatic alkyl radical, an alkoxy radical, an acyl radical, acarbamyl radical, a carboxyl radical or a nitro radical. Aliphatic alkylradicals are defined herein to inelude straight and branched chain alkylradicals having from 1 to 8 carbon atoms such as methyl, ethyl,isopropyl, tert-vutyl, n-amyl, octyl and the like.

Other useful diazonium salts include p-aminobenzenediazonium saltshaving the formula as described above wherein M is either an aminoradical including substituted amino radicals or a thioether radical suchas described above, and wherein the benzene nucleus is unsubstituted orsubstituted in at least one of the 2-position and the 5-position witheither an aliphatic alkyl radical or an alkoxy radical. This class ofuseful diazonium salts can be represented by the formula:

wherein:

(1) D is either a sulfur atom or a radical having the formula NR (2) Rwhen taken alone, is either a hydrogen atom when D is NR or a loweraliphatic alkyl radical, a lower alkoxy radical, an acyl radical havingthe formula:

wherein T is either an aryl radical or an alkyl radical as describedelsewhere herein, or a phenyl radical when D is either a sulfur atom orNR 3) R when taken alone, is either a hydrogen atom, a lower alkylradical or a lower alkoxy radical,

(4) R and R when taken together, complete a divalent radical having theformula:

O CH

31 RB acr R 1 wherein:

(1) Each of R and R when taken alone, is a lower alkyl radical,

2) R and R when taken together, are the number of carbon and heterooxygen atoms necessary to complete a morpholino radical,

(3) Each of R and R is a hydrogen atom, a lower alkyl radical or a loweralkoxy radical, and

(4) Z is either a chlorozincate anion, a fluoroborate anion, a sulfateanion, a phosphate anion, or a chlorostannate anion.

Other well suited benzene diazonium salts are the fluoroborate saltswherein:

(1) R and R are alkoxy radicals when R and R complete a morpholinoradical, and

(2) R and R are each a hydrogen atom when R and R are each a lower alkylradical.

Illustrative of the suitable diazonium salts are compounds as the saltsof l-diazo-2,5-dimethoxybenzene; 1-diazo-2,5-diethoxyb enzene;1-diazo-4-chloro-2,S-diethoxybenzene; 4-diazo-2,5-dimethoxybiphenyl; 4-diam-2,5 ,4-triethoxybiphenyl; 1-diazo-4-dimethylaminobenzene;l-diazo-4- (diethoxyamino) benzene; 1-diazo-4- [bis (hydroxypropyl)amino] benzene; l-diazo-4- (N-methyl-N-allylamino benzene; 1-diazo-4-(diamylamino benzene; 1-diazo-4- (oxazolidino) benzene; 1-diazo-4-(cyclohexylamino benzene; 1-diazo-4- (9-carbazolyl benzene; 1-diazo-4-(dihydroxyethylamino) -3-methylbenzene;1-diazo-4-dimethylamino-3-methylbenzene; 1-diazo-2-methyl-4-(N-methyl-N-hydroxyp ropylamino benzene;l-diazcr4-dimethylamino-3-ethoxybenzene;1-diazo-4-diethylamino-3-chlorobenzene; l-diazo-Z-carboxy-4-dimethylaminob euzene; 1-diazo-3- Z-hydroxyethoxy)-4-pyrrolidinobenzene; 1-diazo-2,5-diethoxy-4-acetoxyaminobenzene;1-diazo-4-methylamino- 3 -ethoxy-6-chlorobenzene; 1-diazo-2, 5-dichloro-4-benzylaminob enzene; l-diazo-4-phenylaminobenzene;1-diazo-4-morpholinobenzene; 1-diazo-4-morpho1ino-3-methoxybenzene;1-diazo-4-morpholino-2,5 -dimethoxyb enzene; 1-diazo-4-morpholino-2-ethoxy-5 -methoxybenzene; 1-diazo-4-morpholino-2,5-dibutoxyb enzene;1-diazo-2,5-diethoxy-4-benzoylaminobenzene;1-diaZo-2,S-dibutoxy-4-benzoylaminobenzene;1-diazo-4-ethylmercapto-2,S-diethoxybenzene;1-diazo-4-tolylmercapto-2,S-diethoxybenzene such and the like, as Wellas mixtures thereof.

In addition to the above-mentioned p-aminobenzene diazonium salts,similar substituted diazonium salts are also useful. Any or all of theremaining carbon atoms can be substituted with a variety of substituentssuch as a lower alkyl radical of 1 to 5 carbon atoms, a lower alkoxyradical having 1 to 5 carbon atoms, an aryl radical such as phenyl,tolyl, etc., a halogen atom such as chlorine, etc., a heterocyclicradical such as morpholino, etc., a nitro radical, an amino radical,including substituted amino radicals, and the like.

Azo and azomethine type polymeric dyes are representative of a widevariety of polymeric dyes which are suitable for use in the formation ofliquid developer compositions in accordance with this invention.Thiazone type polymeric dyes can be formed usingN-acrylamidomethylthionine prepared as described in J. Polymer Sci.,A-6, 2967 (1968) and copolymerizing with styrene or other suitablemonomer to produce a blue polymeric dye. Triphenylmethane type dyes can'be prepared using the polymerizable triphenylmethane, base,bis(p-aminopheny1)-p-vinyl-phenyl carbinol, Ber. 93, 1899 (1960), andcopolymerizing with styrene or some other monomer. Anthraquinone typepolymeric dyes can be prepared by copolymerizing glycidyl methacrylatewith styrene or acrylic esters and treating the resultant polymer With1,4-diaminoanthraquinone to give a blue dye (GA. 65 13853). Polymericstyryl dyes are prepared, for example, by copolymerizing vinyl phthalicanhydride with styrene or other suitable monomers and treating theproduct with 2-(4-hydroxyethoxystyryl)pyridinium chloride to form ayellow dye.

In addition to the various coupling procedures described above, suitablepolymeric dyes can be formed by copolymerizing a dye containing apolymerizable group with a suitable monomer. For example, suitablematerials can be prepared by copolymerizing azo and anthraquinone 6 dyescontaining a polymerizable group, said polymerizable group having thegeneral formula:

wherein R represents a hydrogen atom or a lower alkyl radical havingfrom 1 to 3 carbon atoms such as methyl, ethyl, isopropyl, etc. Suitablematerials for copolymerizing with the above dyes would include thefollowing: vinyl chloride, vinyl sulfonic acid, styrene and derivativessubstituted on the benzene nucleus, acrylic acid, u-chloroacrylic acid,acrylic acid esters, methacrylic acid esters of methacrylic acid,a-chloroacrylic acid esters, esters of maleic acid, fumaric acid,crotonic acid, maleic anhydride, acrylamide or acrylonitrile, esters ofvinyl alcohol and of allyl alcohol With organic acids, vinyl ethers,N-vinylcarbazole, N-vinylpyrrolidone, vinylidene chloride or vinylidenecyanide. Mixtures of the above dyes can be used as can mixtures of theabove polymerizable groups.

As seen above, useful polymeric dyes can be prepared in severaldifferent ways; however, the resultant materials have features incommon. The final polymeric dyes typically have a linear backbone towhich are attached pendant side chains containing a chromophore. Thenumber of side chains attached to the linear backbone can be very large,but the number of side chains containing a chromophoric moiety canbequite small in comparison. The chromophoric moieties which arefunctional in the useful polymeric dyes can include azo, azomethine(including indoaniline), thiazine, triphenylmethane, styryl,anthraquinone, oxazine and the like dye moieties, with azo andazomethine dye moieties being among the preferred. The chromophoricmoiety typically comprises only a minor portion of the polymeric dye. Ingeneral, the polymeric dyes used in this invention contain from about 5to about 50% by weight of the chromophoric moiety.

Where desired, the electrostatic charge polarity of the markingparticles of the present invention can be enhanced or altered by theaddition of suitable charge control agents. A variety of materials canbe used as charge control agents. Illustrative of suitable materialswould be polyoxyethylated alkyl surfactants such as polyoxyethylatedalkylamine, polyoxyethylene palmitate, polyoxyethylene stearate, etc.Other useful materials are magnesium and heavier soaps of fatty andaromatic acids as described in Beyer US. Pat. No. 3,417,019. Usefulmetal soaps include cobalt naphthenate, magnesium naphthenate, manganesenaphthenate, zinc resinate, calcium naphthenate, zinc linoleate,aluminum resinate, isopropyl titanium stearate, aluminum stearate, andothers many of which are also described in US. Pat. No. 3,259,581.

The polymeric dyes of the present invention can be used alone or inconjunction with a colorless resin. Suitable colorless resins can beused if desired to facilitate binding of the colorant to the surface tobe developed. Suitable resinous materials for this purpose can beselected from a wide variety of substances. The following areillustrative of suitable materials: rosins, including hydrogenatedrosins and esters of hydrogenated rosins; alkyl methacrylate copolymershaving from 1 to 18 carbon atoms in each alkyl moiety, such as isobutylmethacrylate, n-butyl methacrylate copolymers, etc.; phenolic resins,including modified phenolic resins such as phenol formaldehyde resins;pentaearythritol phthalate, coumarone-indene resins; ester gum resins;vegetable oil polyamides; alkyd resins, including modified alkyd resinssuch as soya-oil-modified and linseed-oil-modified alkyds, phthalic,maleic and styrenated alkyds, etc., and the like. Suitable colorlessresins are typically used in amounts between about 25 to 75% by weightbased on the total toner composition.

Developers according to the present invention are typically prepared byforming suitable size particles of the polymeric dye and any otherdesired addenda and dispersing these particles in an insulating liquid.The marking particles can be prepared by various methods. Two convenienttechniques for producing these particles are spray-drying ormelt-blending followed by grinding. The spray-drying technique involvesdissolving the polymeric dye typically in a volatile organic solventsuch as dichloromethane. This solution is then sprayed through anatomizing nozzle using a substantially nonreactive gas such as nitrogenas the atomizing agent. During atomization, the volatile solventevaporates from the airborne droplets, producing particles of polymericdye. The ultimate particle size is determined by varying the size of theatomizing nozzle and the pressure of the gasous atomizing agent.conventionally, particles of a diameter between about A and about 25microns are used, with particles between about 1 and 15 microns beingpreferred, although both larger and smaller particles can be used wheredesired for particular developer conditions or developer compositions.

As mentioned above, suitable toner particles can also be prepared bymelt-blending. This technique involves melting a polymeric dye and anyof the other desired additives. The materials can be readily melted onheated compounding rolls which are also useful to stir or other- Wiseblend the various ingredients. After thorough blending, the mixture iscooled and solidified. The resultant mass is then broken into smallpieces and finely ground to form a free-flowing powder of tonerparticles. The resultant particles usually range in size from about A toabout 25 microns as above.

After formation of the toner particles utilizing the polymeric dyes ofthe instant invention, the particles are dispersed in a suitable carriervehicle. Carrier liquids which may be used to form the presentdevelopers can be selected from a wide variety of materials. Preferably,this liquid has a low dielectric constant and a very high electricalresistance such that it will not disturb or destroy the electrostaticlatent image being developed. In general, useful carrier liquids shouldhave a dielectric constant of less than about 3, should have a volumeresistivity of greater than about 10 ohm-cm. and should be stable undera variety of conditions. Suitable carrier liquids include halogenatedhydrocarbon solvents, for example, fluorinated lower alkanes, such astrichloromonofiuoromethane, trichlorotrifluoroethane, etc., having atypical boiling range of from about 2 to about 55 C. Other hydrocarbonsolvents are also useful such as isoparaffin hydrocarbons having aboiling range of from about 150 to about 185 C. such as Isopar G (HumbleOil and Refining Co.). Additional useful carrier liquids includepolysiloxanes, odorless mineral spirits, octane, cyclohexane, etc.Another property of the carrier liquid is that it cannot be a completesolvent for the polymeric dye. When colorless resins are also used, asmall degree of solubility of the resin in the carrier can be tolerated.

Developer compositions can also be prepared by dissolving the presentpolymeric dyes in a small amount of solvent followed by dispersing thissolution in a nonsolvent for the polymeric dye. Useful developercompositions prepared by suitable means typically have from about 0.1 toabout 10 g. of toner material per liter of carrier liquid, with apreferred concentration of about /2 to g./l.

The following examples are included for a further understanding of theinvention.

EXAMPLE 1Yellow polymeric dye A mixture of 56 g. of styrene, 14 g. ofp-aminostyrene and 2 g. of azobisisobutyronitrile is flushed withnitrogen and heated to 100 C. for 16 hours. This gives solid poly(styrene-co-p-arninostyrene) with an amine equivalent weight of 595.Next, 9 g. (.015 mole of amine) of the above copolymer are dissolved in40 ml. of pyridine to which is added 6.5 g. (.020 mole) ofa-pivalyl-4-chlorosulfonylacetanilide. The mixture is stirred for 2hours at 65 C. and then stirred overnight at 45 C. After dilution with50 m1. of acetone, the solution is poured slowly into water toprecipitate the polymer. Reprecipitation from an acetone solution intoisopropyl alcohol gives the coupler polymer, poly{a-pivalyl 4 [N (4vinylphenyl) sulfamyl]acetanilide-co-styrene}. To a solution of 2.6 g.(0.0030 mole) of the polymeric coupler in 40 ml. of peroxide-freetetrahydrofuran is added, with stirring, 30 ml. of a sodiumcarbonate-sodium bicarbonate (0.5 molar each) aqueous buffer solution.To this mixture is added 0.96 g. (0.0045 mole) of4-diethylamino-2-methylaniline hydrochloride in 5 ml. of water followedby the addition of 1.6 g. (0.006 mole) of potassium persulfate in 15 ml.of water. The mixture is stirred for one-half hour. The product isprecipitated by pouring the mixture into vigorously stirred water. Thepolymeric dye is collected, partially dried, and redissolved in 40 ml.of tetrahydrofuran. The solution is filtered and the polymer againprecipitated in Water. The yield of poly{u(4-diethylamino-Z-methylphenylimino) a pivalyl 4[N-(4-vinylphenyl)sulfamyl]acetanilide-co-styrene} is 2.8 g. Theabsorption maximum of a chloroform solution of this yellow dye is 450nm.

EXAMPLE 2-Magenta polymeric dye A mixture of 126 g. of styrene and 14 g.of p-arninostyrene are copolymerized as in Example 1. To 20 g. (0.017mole) of the poly(styrene-co-p-aminostyrene) in ml. of tetrahydrofuranand 3 ml. of pyridine is added 6.2 g. (0.018 mole) of1-phenyl-3-(2-chlorocarbonylbenzamido)-5-pyrazolone in 60 ml. oftetrahydrofuran at 10 C. The mixture is stirred at 40 to 50 C. for 2hours and poured into water to precipitate the product. Re precipitationfrom methylene chloride solution gives 15 g. of the coupler,poly[N-(4-vinylphenyl)-N'-(l-phenyl- 5-pyrazolon-3-yl)phthalamicacid-co-styrene]. This polymeric coupler is converted to a magenta dye,poly{N-(4- vinylphenyl)-N'-[4 (4 diethylamino-Z-methylphenylimino) 1phenyl-5-pyrazolon-3-yl]phthalamic acid-c0- styrene}, in the same manneras described for the yellow dye of Example 1. The absorption maximum ofa chloroform solution of this polymeric dye is 540 nm.

EXAMPLE 3-Cyan polymeric dye A solution of 45 g. of styrene, 5 g. ofN-(3,5-dichloro- 2-hydroxy-4-methylphenyl)acrylamide and 2.5 g. of a20-bisisobutyronitrile in 20 ml. dimethylformamide is flushed with nitrogenand heated at 60 C. for 20 hours. The resultant copolymer,poly[N-(3,5-dichloro-2-hydroxy 4- methylphenyl)acrylamide-co-styrene],is recovered by precipitation in methanol. The polymeric coupler isconverted to a cyan dye,poly{6-acrylamido-2-chloroN-[(4-diethylamino-2-methyl)phenyl] 3 methyl pbenzoquinone imine-co-styrene}, in accordance with the couplingprocedure of Example 1. The polymeric dye in a chloroform solution hasan absorption maximum at 665 nm.

EXAMPLES 4-6 Each of the dyes produced according to Examples 1 through 3is dissolved in a separate portion of dichloromethane using 1 g. of dyein about 84 g. of solvent. The solution is then spray-dried through apneumatic atomizing nozzle using nitrogen gas at 10 p.s.i.g. as theatomizing gas. The solvent is dried off at room temperature to producetoner particles having an average particle size of about 2 microns.Developer compositions A, B and C are prepared using the toner particlescontaining the polymeric dyes of Examples 1, 2 and 3, respectively. A0.5 g. portion of the spray-dried toner particles is dispersed in 250ml. of an Isopar G (supra). Each of the three developers is then used todevelop an electrostatic charge pattern on an electrophotographicelement. This element is comprised of a conductive support havingthereon a photoconductive layer containing an organic photoconductordispersed in a polycarbonate binder. This element is uniformly chargedby subjecting it to a negative polarity corona discharge in the dark.The element is given an imagewise exposure which causes dissipation ofthe charge in the exposed areas thus forming an electrostatic chargepattern. The element is then placed into contact with one of the abovedevelopers. This procedure is repeated for all three developers using adifferent element each time. The resultant positive images are notfixed; however, exposure to dichloromethane vapor for a brief periodcauses the images to be fixed. All three images are of good quality. Theabove procedure is repeated with the yellow developer A after reducingthe concentration of 0.5 g. of dye per liter of Isopar G. The diluteddeveloper still produces images of acceptable density. Developer Cremains stable for over a month with only a slight amount of a sedimentappearing. This settling does not appear to be the result ofagglomeration, as the settled particles are readily redispersed byshaking.

EXAMPLE 7-Azo polymeric dyes The polymeric coupler, poly{upivalyl-4-[N-(4-vinylphenyl)-sulfamyl] acetanilide-co-styrene}, ofExample 1 is added to a molar excess of an alkaline aqueous solution of4-diethylaminobenzene-diazonium zinc chloride double salt. The mixtureis stirred for about 30 minutes at room temperature and a yellowpolymeric dye (No. 4), poly{a- (4-diethylaminophenylazo) apivalyl-4-[N-(4-vinylphenyl) sulfamyl] acetanilide-co-styrene}, isprecipitated. This same procedure is repeated using the polymericcoupler of Example 2 to produce a magenta dye (No. poly{N-4 vinylphenyl)N [4-(4-diethylaminophenylazo) 1 phenyl 5 pyrazolon 3 -yl]phthalamicacidco-styrene}. Similarly, the polymeric coupler, poly[N-(3,5-dichloro-2-hydroxy-4-methylphenyl) acrylamide costyrene], of Example 3is treated with a molar excess of the above diazonium salt underalkaline conditions to form a cyan dye (No. 6), poly[6-acrylamido 2chloro- 4 (4 diethylaminophenylazo) 3 methylphenol costyrene]. Polymericdyes Nos. 4, 5 and 6 are each dissolved in dichloromethane andspray-dried as in Examples 4-6 to produce dye particles. About /2 g. ofdye is dispersed in 250 ml. of Isopar G to form three developercompositions D, E and F, respectively. Each of these developers is thenused to develop an electrostatic charge pattern as described in Examples4-6. The resultant images are all of good quality.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

We claim:

1. In an electrophotographic process wherein an elec trostatic chargepattern is formed and liquid developed, the improvement comprising usinga liquid developer comprised of an electrically insulating hydrocarboncarrier liquid having a dielectric constant of less than about 3 and avolume resistivity of greater than 10 0hm-cm., said liquid havingdispersed therein marking particles comprising at least one polymericdye, said polymeric dye consisting essentially of the reaction productof (1) a polymeric coupler having a linear backbone chain to which areattached pendant side chains containing a coupling unit selected fromthe group consisting of an open chain active methylene coupling moiety,a. cyclic active methylene coupling moiety, and a phenolic nucleusbearing an active methine group, and (2) a member selected from thegroup consisting of diazonium salts and oxidation products of colorcoupling aromatic primary amine developing agents, said markingparticles having a particle size Within the range of from about 0.25 toabout 25 microns and wherein said marking particles are present in saidliquid developer in a concentration of about 0.1 to 10 grams per literof developer.

2. The invention as described in claim 1 wherein said oxidation productdeveloping agents are selected from the group consisting of oxidizedp-phenylene diamines and oxidized p-aminophenols.

3. The invention as described in claim 1 wherein said diazonium salt isa benzene diazonium salt.

4. The invention of claim 1 wherein said diazonium salt is ap-amino-benzene diazonium salt.

5. The invention of claim 1 wherein said polymeric dye is comprised of alinear backbone chain formed of a vinyl polymer.

6. The invention of claim 1 wherein said linear backbone chain containspolymerized monomers selected from the group consisting of styrene,alkyl acrylates having from about 4 to 18 carbon atoms in the alkylmoiety, vinyl acetate, vinyl chloride, vinyl alkyl ether having fromabout 4 to 18 carbon atoms in the alkyl moiety, alkyl methacrylatehaving from about 4 to 18 carbon atoms in the alkyl moiety and mixturesthereof.

7. The invention of claim 1 wherein said marking particles contain fromabout 25 to by weight of a colorless resin.

8. The invention of claim 1 wherein said polymeric dye is selected fromthe group consisting of poly{ 6acrylamido-2-chloro-N-(4-diethylamino-2-metlily phenyl] -3 -methyl-p-benzoquinoneimine-co-styrene},

poly{N-(4-vinylphenyl)-N'-[4- (4-diethylamino-Z-methylphenylimino)-1-phenyl-5-pyrazolon-3 -yl]-phthalamicacid-co-styrene},

poly{ a-(4-diethylamino-2-me thylphenylimino)-ot-pivalyl-4-[N-(4-vinylphenyl)sulfamyl]-acetanilide-costyrene},

PO1y{0t- (4-diethylaminophenylazo -a-pivalyl-4- [N- (4- vinylphenyl)sulfamyl] acetanilide-co-styrene},

poly{ N- (4-vinylphenyl) -N'- [4- (4-diethylaminophenylazo)-1-phenyl'5-pyrazolon-3 -yl] -phthalamic acidco-styrene},

poly 6-acrylamido-2-chloro-4-(4-diethylaminophenylazo)-3-methylphenol-co-styrene].

References Cited UNITED STATES PATENTS 3,337,288 8/ 1967 Horiguchi et al8--4 3,190,850 6/1965 Burke 26038 3,135,695 6/1964 York 252-62.13,102,821 10/1963 Johnson 25262.1 3,639,244 2/1972 Machida et al.252--62.1 3,639,243 2/ 1972 Okuno et al. 25262.1

FOREIGN PATENTS 1,133,689 11/1968 Great Britain 8-8 1,016,072 1/ 1966Great Britain 25262.1 877,402 1961 Great Britain 8-8 852,646 1960 GreatBritain 8-8 NORMAN G. TORCHIN, Primary Examiner I. P. BRAMMER, AssistantExaminer U.S. Cl. X.R.

